Nowadays, with the rapid development of network technologies, communications networks become more centralized, complex, and intelligent. In networking of a communications network, as a quantity of network devices continuously increases, higher requirements are imposed on performance of the network devices and a coupling degree between the network devices. Generally, a communications network provides a bi-directional service flow transmission service. Inevitably, an asymmetric delay (English full name: Asymmetric delay) exists between a forward service flow direction and a reverse service flow direction, that is, asymmetry exists between a delay generated in the forward service flow direction and a delay generated in the reverse service flow direction. For example, a bi-directional asymmetric delay variation exists during data transmission on all such communications networks as a wireless communications network (for example, a mobile communications network), a wired communications network (for example, an asymmetric digital subscriber line (English full name: Asymmetric digital subscriber line, English acronym: ADSL), a very-high-data-rate digital subscriber line (English full name: Very-high-data-rate digital subscriber line, English acronym: VDSL)), or a dedicated communications network (for example, a power communications network).
Using mobile communications networks as an example, a clean, centralized processing, collaborative radio, and real-time cloud radio access network (English full name: Clean, centralized processing, collaborative radio, and real-time cloud radio access network, English acronym: C-RAN) is used in a modern mobile communications network. The C-RAN has characteristics such as centralization, collaboration, and virtualization. In a C-RAN architecture, centralization of a baseband control unit (English full name: Baseband control unit, English acronym BBU) increases the distance between a remote radio unit (English full name: Remote radio unit, English acronym: RRU) and the BBU. Therefore, a corresponding transport network needs to be deployed to implement data transmission between the RRU and the BBU. Such a transport network is referred to as a fronthaul network (English full name: FrontHaul). The fronthaul network may be built using optical transport devices or packet switched devices. Inevitably, a bi-directional asymmetric delay variation would be brought into a bi-directional data transmitting and receiving path.
Based on the above, there is a strict requirement on the range of a bi-directional asymmetric delay variation of data transmission on a communications network, and if the variation exceeds a limit, abnormal user communication is caused.